System for collecting oil on water

ABSTRACT

A system for collecting oil on water comprises an oil boom ( 1 ) and a floating collection container ( 2 ), which is connected to an opening ( 4 ) in the boom by a pumping hose ( 3 ). The pumping hose ( 3 ) is flexible so that it can follow the wave motions of the water and is provided with non-return valves, making the flow ( 18 ) in the pumping hose unidirectional. The distance between the opening ( 4 ) in the boom and the collection container ( 2 ) is adjustable by tension members ( 8 ) in order for the excess length or slack in the pumping hose ( 3 ) to be adjusted to the prevailing wave height or length conditions.

BACKGROUND OF THE INVENTION

In connection with oil spill protection operations where one has triedto use traditional oil booms and skimmers in order to collect oil fromthe sea surface, it has proven difficult to keep the oil in the oil boomlong enough for the skimmer to transfer it to a tanker or the like. Thereason is that if the relative velocity between the boom and the waterexceeds about 1 knot, the oil has a tendency to escape below the boom.This situation is aggravated in waves, and even the best of the existingoil booms will in reality have problems in keeping the oil contained inwave heights above 3 meters.

DESCRIPTION OF THE PRIOR ART

In order to alleviate these problems, an oil collecting system haspreviously been suggested in DE-A-2936151 where one can transfer the oilcontinuously from the boom to a floating, generally closed separationcontainer which is towed behind the boom and is connected to an openingat the bight of the boom by means of a tubular member. The separationcontainer is in the bottom provided with one or more openings so thatwater can escape, and the container is sufficiently large for anymixture of oil and water to have sufficient retention time to undergo agravity separation. As the container is filled with oil, it may beemptied over into a trailing collection container.

A disadvantage in the system according to DE-A-2936151 is that thetowing forces of the separation and collection containers aretransmitted directly to the oil boom via the tubular member. Theseforces have an impeding effect on the ability of the oil boom to followthe motions of the sea. Furthermore, motor driven propellers arearranged both in the tubular member and in the connection between theseparation and collection containers in order to provide transportationof the water and oil. These propellers will cause a strong stirring andmixing of the oil and water that will complicate the desired separationof these liquids.

In order to avoid or reduce these problems, it is suggested according tothe invention to modify the previously suggested system in such a waythat the tubular member will function as a pump under the influence ofthe wave motion of the water.

SUMMARY OF THE INVENTION

This is obtained according to the invention by forming the tubularmember in a flexible manner so that it will be able to follow the wavemotion of the water and thereby act as a pump, for instance by it beingprovided internally with means restricting the flow therein from theboom towards the collection container. Such means can be non-returnvalves of different shapes, so that a kind of peristaltic effect isobtained.

In order for the tubular member, in the following also called thepumping hose, to be able to follow the motions of the sea as efficientlyas possible, it is suggested according to the invention to transmit thenecessary towing forces to the collection container by means of separatetension members. The tension members can be run from the collectioncontainer to e.g. a point on the boom spaced from its opening, ordirectly to a towing vessel.

The length of the tension members is preferably adjustable, i.a. inorder to make the excess length or the slack in the pumping hosevariable for the adjustment to the prevailing wave conditions, i.e. thelength and height of the waves.

The expected wave length will also influence the length of the pumpinghose, this length being preferably at least one half of the wave lengthof the longest waves to be expected to some extent.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention it will be described moreclosely with reference to the exemplifying embodiments schematicallyshown in the appended drawings, where

FIG. 1 is a perspective view showing schematically parts of the mainelements comprised by the system according to the invention in floatingcondition,

FIG. 2 shows schematically a plan view of a first embodiment of theinvention while in use,

FIG. 3 shows a view similar to that of FIG. 2 of a second embodiment ofthe invention,

FIG. 4 shows a view similar to FIG. 2 of a third embodiment of theinvention, and

FIG. 5 shows schematically, partly in section, a portion of a pumpinghose according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The system according to the invention illustrated in FIG. 1 comprises anoil boom 1, a floating collection container 2 and a generally tubularmember 3 connecting the oil boom 1 and the collection container 2. Theoil boom has an opening 4 (not visible) where the tubular member 3 isconnected, so that a flow communication is formed between the bight ofthe boom and the collection container.

Both the collection container 2 and the tubular member 3 are providedwith stiffening ribs 5 and 6, respectively, which e.g. can have the formof inflatable rings concurrently serving as buoyancy bodies. The tubularmember 3, which also is called a pumping hose, is connected to thecollection container 2 by means of a quick release coupling 7, e.g. inthe form of a muff coupling, where one of the two mutually overlappingelements is generally rigid and the other is flexible, the flexibleelement being clamped on the rigid element by means of a tighteningdevice, e.g. in the form of an inflatable ring.

Tension members, e.g. in the form of ropes or wires, will extend betweenthe coupling 7 and the boom 1 and/or a towing vessel. These members arenot shown in FIG. 1, but are exemplified in FIGS. 2-4. Both thecollection container 2 and the pumping hose 3 may be made of flexiblematerial, e.g. a plastic covered textile, their shape being maintainedby means of the ribs 5,6. The bottom of the collection container may beprovided with one or more closeable openings in order for water toescape during the collecting operation, and the container may further beprovided with a hose connection (not shown) at the end in order topermit the suction of oil from the container while it is in use.

It is also referred to FIGS. 2-4, where three different towingconfigurations for the system according to the invention areillustrated. Here, similar elements are designated by the same referencenumerals.

FIG. 2 shows the oil boom 1, the collection container 2 and the pumpinghose 3, generally in accordance with FIG. 1. In addition, the figureshows a tension member 8 running from the coupling via two attachmentpoints 9 on the boom and back to the coupling 7. The attachment pointsmay have the form of snatch blocks through which the tension member isrunning in order to provide some control of the geometry of the boom.However, the tension member 8 may be provided with stoppers that willabut against the snatch blocks if the boom should try to assume anundesirable geometry. The snatch blocks 9 may be attached to the tensionrelieving member of the boom, usually being a chain.

FIG. 2 furthermore shows a towing vessel 10 towing the left part of theboom 1. The right part of the boom is also connected to a vessel (notshown) in a manner known per se. From a winch 11 on the towing vessel 10a rope 12 extends transversally over to the right part of the boom 1,the rope being attached to the boom by means of a netting crowfoot 13which distributes the tension from the rope 12 to a larger portion ofthe boom. By means of the winch 11 the boom bight may be varied, e.g. inrelation to the towing velocity.

It will be noted that the length of the tension member is adjusted sothat the pumping hose 3 has an excess length so that it can assume awavy shape and thus follow the wave motions of the water withoutappreciable tension occurring therein.

FIG. 3 shows an embodiment where the tension member 8 at one end isattached to the right part of the boom at the netting crowfoot 13. Thetension member runs over a pulley, e.g. in the form of a snatch block14, and from there to a winch 15 on the towing vessel 10. By means ofthe winch 15 the length of the tension member 8, may be varied, therebyvarying the slack or excess length of the pumping hose 3. This makes itpossible to adjust the length of the pumping hose to the prevailing waveconditions, i.e. the height and length of the waves.

In the embodiment in FIG. 3 there may also be arranged safety lines (notshown) between the coupling 7 and the boom near the opening 4. Suchsafety lines must be shorter than the pumping hose 3 and will becomefunctional if one, by extending the tension member 8, should wish tomake the bight of the boom more pointed, for instance for quickening theflow of oil towards the opening 4.

FIG. 4 shows an embodiment where the towing force for the collectioncontainer 2 is transmitted directly to the towing vessel 10. In thiscase a safety line 16 is used to prevent the boom bight from beingpulled so far from the container 2 that the pumping hose 3 will notretain the necessary freedom of movement.

As mentioned previously, the pumping hose 3 may have different designsand for instance be provided with internal non-return valves. A possibledesign of such a non-return valve is schematically suggested in FIG. 5.Here, the valve 17 has the shape of a funnel of flexible material, e.g.a fabric material, which will permit flow in the direction of the arrow18, but will collapse and close if the flow should try to move in theopposite direction. In order to prevent the funnel from folding back onitself during flow in the wrong direction, the pointed end of the funnelis connected to a tension member 19 attached to a suitable point on theinside of the pumping hose.

Also other forms of non-return valves can advantageously be used in thepumping hose 3 according to the invention. For instance, double flapvalves may be used, preferably such valves that have integrally castsemi-circular flaps hinged along a common diameter by means of filmhinges cast integrally with the valve flaps. Such valves will open andclose at very low pressure differences and will, due to their simplestructure, be reliable and essentially maintenance free. It will beunderstood that the pumping hose 3 does not have to consist of a singlecontinuous length, but may be put together from several segments, eachcontaining for instance a non-return valve, so that the pumping hoseeasily can be made to the desired length and taken apart for repair,maintenance or cleaning.

Even though the invention has been described above with reference tospecial exemplifying embodiments, it will be clear to the skilled personthat it may be varied and modified in a number of ways within the frameof the appended patent claims. For instance, the pumping hose 3 may begiven a certain axial stiffness in order to prevent that, due to itsexcess length, it should get a fold or bend that would hinder flowtherethrough. Such a limited axial stiffness, along with the necessaryflexibility, may for instance be obtained by means of longitudinal airfilled canals divided into sections and arranged at the desired waterline. Another alternative is to use a corrugated hose made from asuitable plastic material. In order to facilitate cleaning of the hoseafter use, it may be provided with an internal lining, e.g. of filmmaterial, which may be removed and destroyed after final use.

What is claimed is:
 1. A system for collecting oil on water, comprisingan oil boom adapted to be towed against waves moving in the water so asto form a bight where the oil will tend to concentrate, said waveshaving a crest-to-crest wave length, and a floating collection containerwhich in use of the system is located behind the boom and has an inletat the water level which, by means of a generally tubular member, isconnected to an opening in the boom at the bight thereof, characterisedin that the generally tubular member comprises a floating flexible hoseprovided with means making flow therein substantially uni-directionalfrom the opening to the container, and that tension members are arrangedfor holding the collection container at a predetermined distance fromthe opening in the boom to permit the flexible hose to substantiallyfreely follow the wave motions of the water, whereby oil is transporteddue to the wave motion action on the hose from said opening to thecontainer.
 2. A system according to claim 1, characterised in that saiduni-directional flow means are comprised by at least one non-returnvalve.
 3. A system according to claim 2, characterised in that at leastone of the tension members is connected directly to a towing vessel. 4.A system according to claim 3, characterised in that said tension memberis connected to a winch on the towing vessel and runs over a pulleyarranged on or near the collection container and further to a point onthe boom on the opposite side of the bight of the boom with respect tothe towing vessel.
 5. A system according to claim 2, characterised inthat the flexible tubular member is comprised substantially of a hose offabric material and is provided with stiffening rings concurrentlyserving as buoyancy bodies.
 6. A system according to claim 2,characterised in that the tubular flexible member has a lengthcorresponding at least to half the wave length in which the system canfunction.
 7. A system according to claim 2, characterised in that thelength of the tension members is adjustable.
 8. A system according toclaim 2, characterised in that the tension members are connected to theboom at a distance from its opening.
 9. A system according to claim 1,characterised in that the flexible tubular member is comprisedsubstantially of a hose of fabric material and is provided withstiffening rings concurrently serving as buoyancy bodies.
 10. A systemaccording to claim 9, characterised in that at least one of the tensionmembers is connected directly to a towing vessel.
 11. A system accordingto claim 10, characterised in that said tension member is connected to awinch on the towing vessel and runs over a pulley arranged on or nearthe collection container and further to a point on the boom on theopposite side of the bight of the boom with respect to the towingvessel.
 12. A system according to claim 9, characterised in that thetubular flexible member has a length corresponding at least to half thewave length in which the system can function.
 13. A system according toclaim 9, characterised in that the length of the tension members isadjustable.
 14. A system according to claim 9, characterised in that thetension members are connected to the boom at a distance from itsopening.
 15. A system according to claim 1, characterised in that thetubular flexible member has a length corresponding at least to half thewave length in which the system can function.
 16. A system according toclaim 15, characterised in that the length of the tension members isadjustable.
 17. A system according to claim 1, characterised in that thelength of the tension members is adjustable.
 18. A system according toclaim 1, characterised in that the tension members are connected to theboom at a distance from its opening.
 19. A system according to claim 1,characterised in that at least one of the tension members is connecteddirectly to a towing vessel.
 20. A system according to claim 19,characterised in that said tension member is connected to a winch on thetowing vessel and runs over a pulley arranged on or near the collectioncontainer and further to a point on the boom on the opposite side of thebight of the boom with respect to the towing vessel.